docs(module: mention): fix API docs button to bottom

[strawbreey]

PR Checklist

Please check if your PR fulfills the following requirements:

• The commit message follows our guidelines: https://github.com/NG-ZORRO/ng-zorro-antd/blob/master/CONTRIBUTING.md#commit
• Tests for the changes have been added (for bug fixes / features)
• Docs have been added / updated (for bug fixes / features)

PR Type

What kind of change does this PR introduce?

[ ] Bugfix
[ ] Feature
[ ] Code style update (formatting, local variables)
[ ] Refactoring (no functional changes, no api changes)
[ ] Build related changes
[ ] CI related changes
[ ] Documentation content changes
[ ] Application (the showcase website) / infrastructure changes
[ ] Other... Please describe:

What is the current behavior?

Issue Number: N/A

What is the new behavior?

Does this PR introduce a breaking change?

[ ] Yes
[ ] No

Other information

[zorro-bot]

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[codecov]

Codecov Report

Merging #7437 (8242c3f) into master (ed8188a) will increase coverage by 0.01%.
The diff coverage is n/a.

@@            Coverage Diff             @@
##           master    #7437      +/-   ##
==========================================
+ Coverage   91.62%   91.64%   +0.01%     
==========================================
  Files         487      487              
  Lines       16043    16043              
  Branches     2477     2477              
==========================================
+ Hits        14700    14702       +2     
+ Misses       1029     1028       -1     
+ Partials      314      313       -1     

Impacted Files	Coverage Δ
components/tabs/tab-nav-bar.component.ts	87.94% <0.00%> (+0.70%)	⬆️

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[wenqi73]

@strawbreey Thanks!